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Why can't I create an ad hoc 4/5g network between phones? Genuine question. It looks so closed and complex compared to more traditional comms like wifi or eve

Why can't I create an ad hoc 4/5g network between phones? Genuine question. It looks so closed and complex compared to more traditional comms like wifi or even ethernet.

femto 2y ago
The LTE protocol is asymmetric between towers (eNodeB) and phones (UE). You could build srsRAN and run a local eNodeB instance to form a local LTE network. Given that it has a radio that operates in the LTE bands, in theory you might be able to build srsRAN for a phone and run the necessary base station software (eNodeB and EPC) on a phone to form an "ad hoc" network. It wouldn't be truly ad hoc in that the network would still have a base station, just that it would be running on phone hardware. srsRAN wouldn't be running as an application, but would be replacing the firmware in the phone's LTE modem. Edit: Here is a paper by someone who has built an ad hoc LTE network. https://arxiv.org/pdf/1802.09262 https://arxiv.org/pdf/1802.09262 It does exactly the above: using srsRAN (which used to be called srsLTE) to run local base station software (eNodeB+EPC) to get around the asymmetry in the LTE protocol.
bsder 2y ago
> Why can't I create an ad hoc 4/5g network between phones? Because billing. All the complexity in cellular can be traced back to making the system secure the whole way back to SIM cards because there is actual money at stake if the system gets cracked.
- throw5959 2y ago
  What about a "public good" mobile network without any billing, only fair QoS?
  - friendzis 2y ago
    There's limited bandwidth available in the space. 5G is "fast" compared to 4G because 4G effectively saturates terrestrial bandwidth available. Public, unauthenticated network would be too easily DDoSable.
  - deleted 2y ago
    [deleted]
- mytailorisrich 2y ago
  The complexity is actually down to mobility. You can turn your phone on anywhere and it'll work. You can have a call/data session while travelling hundreds of miles and it'll work (usually).
  - rusk 2y ago
    What you suggest could be accomplished with mesh networking. GP is correct in saying the reasons are orthogonal to functional reasons. Phone systems have always been centralised like this. Billing is one aspect, but lawful surveillance is another.
    - mytailorisrich 2y ago
      With respect, if you think that mesh networking would have worked considering the scale and capacity needed, and relevant type of devices then I am afraid this is a case of not knowing what you don't know...
      - throw5959 2y ago
        How do you solve cross talk in congested areas? Made worse by the fact that mesh networks have a significant communication overhead.
        rusk 2y ago
        Cross talk takes place on PHY and by the time you get up to routing it’s all been eliminated
      - rusk 2y ago
        I was using Mesh networking as an example. Obviously it can’t handle heavy load or longer distances well, however it is much more efficient for local point to point. If you like, you can consider just plain old VOIP where the central entity is used for discovery but the actual call may then be routed p2p though not in VoLTE and its successors of course because the media plane is also centrally routed.
kurokawad 2y ago
AFAIK cellular comms aren’t designed to be ad hoc. They require base stations (whose placement is very studied) to build coverage “cells” (cellular). The network is responsible of delivering a QoS, it’s not a best-effort like WiFi. However, if I’m not mistaken 5G has V2V comms (Vehicle to Vehicle) specifically designed for self-driving cars, drones and IoT and that is the most “ad hoc” it can get
solarboii 2y ago
It's complexity is not completely unnecessary. Scale is a huge bitch. Networking between phones, without a common base station, is hard. Harder than WI-FI, because identity is managed centrally and the frecs in use require a license to name some "simple" problems. Cellular comms are not designed to handle this kind of scenario. There has been some work to add inter device connectivity lately, to support many interesting use cases. You can find more looking for "sidelink" or "PC5", but you will not find many phones that implement it. It seems to be mostly focused in vehicular use cases in V2V and V2X scenarios
ianburrell 2y ago
Last time I looked is because the chipset makers haven't implemented LTE Direct. There were a handful of phones with LTE Direct that were oriented towards first responders. 5G also has a peer mode, and I'm trying to figure out if it can be implemented in userspace or has to be done in firmware. My idea is that peer mode would be useful for replacing walkie-talkie or mesh messaging like Meshtastic since everyone has a phone. The range is supposed to be around a mile.

Why can't I create an ad hoc 4/5g network between phones? Genuine question. It looks so closed and complex compared to more traditional comms like wifi or even ethernet.

femto 2y ago

The LTE protocol is asymmetric between towers (eNodeB) and phones (UE). You could build srsRAN and run a local eNodeB instance to form a local LTE network. Given that it has a radio that operates in the LTE bands, in theory you might be able to build srsRAN for a phone and run the necessary base station software (eNodeB and EPC) on a phone to form an "ad hoc" network. It wouldn't be truly ad hoc in that the network would still have a base station, just that it would be running on phone hardware. srsRAN wouldn't be running as an application, but would be replacing the firmware in the phone's LTE modem. Edit: Here is a paper by someone who has built an ad hoc LTE network. https://arxiv.org/pdf/1802.09262 https://arxiv.org/pdf/1802.09262 It does exactly the above: using srsRAN (which used to be called srsLTE) to run local base station software (eNodeB+EPC) to get around the asymmetry in the LTE protocol.

bsder 2y ago

> Why can't I create an ad hoc 4/5g network between phones? Because billing. All the complexity in cellular can be traced back to making the system secure the whole way back to SIM cards because there is actual money at stake if the system gets cracked.

throw5959 2y ago
What about a "public good" mobile network without any billing, only fair QoS?
- friendzis 2y ago
  There's limited bandwidth available in the space. 5G is "fast" compared to 4G because 4G effectively saturates terrestrial bandwidth available. Public, unauthenticated network would be too easily DDoSable.
- deleted 2y ago
  [deleted]
mytailorisrich 2y ago
The complexity is actually down to mobility. You can turn your phone on anywhere and it'll work. You can have a call/data session while travelling hundreds of miles and it'll work (usually).
- rusk 2y ago
  What you suggest could be accomplished with mesh networking. GP is correct in saying the reasons are orthogonal to functional reasons. Phone systems have always been centralised like this. Billing is one aspect, but lawful surveillance is another.
  - mytailorisrich 2y ago
    With respect, if you think that mesh networking would have worked considering the scale and capacity needed, and relevant type of devices then I am afraid this is a case of not knowing what you don't know...
    - throw5959 2y ago
      How do you solve cross talk in congested areas? Made worse by the fact that mesh networks have a significant communication overhead.
      - rusk 2y ago
        Cross talk takes place on PHY and by the time you get up to routing it’s all been eliminated
    - rusk 2y ago
      I was using Mesh networking as an example. Obviously it can’t handle heavy load or longer distances well, however it is much more efficient for local point to point. If you like, you can consider just plain old VOIP where the central entity is used for discovery but the actual call may then be routed p2p though not in VoLTE and its successors of course because the media plane is also centrally routed.

kurokawad 2y ago

AFAIK cellular comms aren’t designed to be ad hoc. They require base stations (whose placement is very studied) to build coverage “cells” (cellular). The network is responsible of delivering a QoS, it’s not a best-effort like WiFi. However, if I’m not mistaken 5G has V2V comms (Vehicle to Vehicle) specifically designed for self-driving cars, drones and IoT and that is the most “ad hoc” it can get

solarboii 2y ago

It's complexity is not completely unnecessary. Scale is a huge bitch. Networking between phones, without a common base station, is hard. Harder than WI-FI, because identity is managed centrally and the frecs in use require a license to name some "simple" problems. Cellular comms are not designed to handle this kind of scenario. There has been some work to add inter device connectivity lately, to support many interesting use cases. You can find more looking for "sidelink" or "PC5", but you will not find many phones that implement it. It seems to be mostly focused in vehicular use cases in V2V and V2X scenarios

ianburrell 2y ago

Last time I looked is because the chipset makers haven't implemented LTE Direct. There were a handful of phones with LTE Direct that were oriented towards first responders. 5G also has a peer mode, and I'm trying to figure out if it can be implemented in userspace or has to be done in firmware. My idea is that peer mode would be useful for replacing walkie-talkie or mesh messaging like Meshtastic since everyone has a phone. The range is supposed to be around a mile.